Watch out for heartworm disease

Heartworm disease has been reported in all 50 states. The parasites spread when an animal is bitten by a mosquito carrying microscopic heartworm larvae. Learn how to protect your animals from infection.

What animals can be infected by heartworms?

Infections have been confirmed in dogs, cat, wolves, coyotes, foxes, ferrets and sea lions. Though humans can contract heartworms, the worms cannot establish themselves in the human body and will die on their own.

Dogs and cats react differently to heartworms. According to the American Heartworm Society (AHS), 100 percent of dogs become infected when exposed to infective larvae. Cats are partially resistant to heartworms. Only 60 to 90 percent of cats become infected after exposure. In cats, the worms are more likely to infect just the lungs and not the heart. Heartworms are potentially fatal in both species.

What are heartworms, anyway?

Heartworms are from a phylum of roundworms called nematodes. The scientific name for heartworms is Dirofilaria immitis. Heartworms feed off an organism’s blood and occupy the right chamber of the heart. They can also infect the pulmonary arteries.

Researchers have found that heartworms are themselves infected with a bacterium called Wolbachia pipientis. The bacterium can cause inflammation in an animal when the heartworms die in the animal’s body.

What are the symptoms of infection?

Infected dogs may have a persistent cough, reduce appetite, weight loss and fatigue after moderate exercise.

Diagnosing heartworms can be difficult in cats because the symptoms mimic other feline diseases. Symptoms include vomiting, difficulty or rapid breathing, gagging, lethargy and weight loss.

To make an official diagnosis, a veterinarian can administer a blood test, x-ray or ultrasound. A positive blood test will show antigens or heartworm larvae, but these signs will not show up until about seven months after infection. If a veterinarian suspects heartworm infection, he or she might do an ultrasound or take x-rays to detect heartworms in the heart or lungs.

How can I prevent infection?

Heartworms are potentially fatal, and treating infections can be very expensive. To prevent infections, the AHS recommends that animal owners protect their pets using monthly tablets, chewables or topicals. These products are available for cats and dogs. There is also a six-month injectable available for dogs.

There are some misconceptions about infection. Indoor pets are not immune to infection. If a mosquito can fly through a window screen or door, your pet is at risk.

What do I do if my animal is infected?

Heartworm in dogs is treatable. There are currently four products approved for treating heartworms in dogs. Adult heartworms in dogs can be treated with a injection of a drug called adulticide. Adulticide is injected into the muscle over a period of time. A dog may have to be hospitalized during treatment. There is a risk that dead worms will block blood flow to the lungs, so dogs should only have mild exercise during and shortly after treatment.

There are currently no products in the United States approved to treat heartworm in cats. Cats are more resistant to heartworms, and their immune systems can often fight off infections on their own. The danger comes when cats try to shed dead worms. The dead worms can cause life-threatening shock and a veterinarian will need to intervene.

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